Polarized electromagnetic device



S@P11- 30, 1952 R. T. FISHER 2,612,544

POLARIZED ELECTROMAGNETIC DEVICE Filed Sept. 16, 1948 3 Sheets-Sheet l Snventor D/c//A/PQ 7.* Fas/15.

677ml v Citto* es Sept. 30, 1952 R. T. FISHER POLARIZED ELECTROMAGNETIC DEVICE 3 Sheets-Sheet 2 Filed Sept. 16, 1948 z5; 22 I Z7 23 Z8 Bu 977m, 049%,

Patented Sept. 30, 1952 POLARIZED vELEC'.lRDlWAGrNETIC DEVICE Richard T. Fisher, I-Iingham, Mass., assignor to Sigma Instruments, Incorporated, a corporation of Massachusetts Application september 1c, 194s, serial Nc. 49,483 Claims. (Cl. 175-339) lThe present invention relates to electromagf netic structures and more particularly to. structures of this character which are suitable for v use as relays of the polarized type.

Among the objects of the invention is the 'provision of a compact and highly efficient polarity responsive electromagnetic structure.` y

-An object of the invention is the provision of a three position electromagnetic structure having a neutral or normal position and which is capable of selectively assuming either of two operated positions in'response to the polarity of van applied energizing current offappropriate magnitude. l

A further object of the invention is the provision of an electromagnetic structure of the character described above which is highly resistant to shock and vibration thereby making it Asuitable for use in aircraft and other vinstallations where adverse operating conditions of this type are likely to be encountered.. Y.

Another object of the invention is to provide an electromagnetic structure in which the movable element thereof is pivoted at a point in close proximity toits center of gravity thereby causing the movable element to besubstantially un- Referring to the drawing:

Fig. 1 is a plan view of a relay embodying the invention;

Fig. 2 is an elevational view, partly broken away; L

Fig. 3 is a sectional view taken along theline 3 3 of Fig. 1, looking in the direction of the of the armature positioning 'mechanism shown inFig. 6;'and

Figs. 8, 9 and l0 are graphical diagrams illustrating theforces acting on the armature for spoolheads vIfyfin'ountecl on amag'netizable core responsive to the effects of linear accelerations imparted to the entire structure. f

it is a feature of the invention that the magnets which are used to obtain the polarity selective response of the movable element have a conformation which enables them to occupy space in the structure which `would ordinarily be vunused. This feature has the advantageous effect of producing a more compact structure than would otherwise be possible.

A further object of the invention is to provide an electromagnetic relay which, when energized various angular positions thereof..

Referring to Fig. 3, a relay is shown `having an Apair of magnetizable pole pieces l5 land I6 are shown secured to oppositeends of core i3 `which are threaded to receive"'s`c1ews Il. Polev by a `current of predeterminedy minimum strength, v

will move completely to its energized position and will build up appreciable contact pressure. Upon a decrease in current intensity below this predetermined strength, the full contact pressure f will be retained, but as thenet armature force approaches zero, the contacts will immediately open completely and without chattering. This type of operation is frequently referred; to as y snap action, `By avoiding contact chatter,

rapid successivel interruptions ofthe controlled electrical circuit are avoided andthe life of the contactsis prolonged.

Other and further obJects will become apparent upon readingthe following specification together with the accompanying drawing forming a part hereof.

pieces i5 and I6 are secured firmly against shouldered portions lilv ofcore i3j`at opposite ends. thereof, the shoulderportions i8' being lheaded over at IQ providing efficient magnetic joints and a permanently assembled unitary' structure; desired, the` shouldered portions i3 may be omitted, the core being positioned bythe contact carriers. f

An armature, designated generally as 2S, is shown comprising two parallel andsubstantially coextcn'sive elongated magnetizabie members' 2| and 22'y joined together, the upper member y2l being curved upwardly a shortvldistance -atits central portion to providev a rspace for the accomodation of armature pivot pin 23 which eX-` tends transversely intermediate mernifer's" 2 l. and 22, and is firmly gripped between these two vmerribers.

l Extending*longitudinally above and adjacent-v to winding l I Yis af pair o'f permanent magnets 213 of substantiallytriangular. cross'fsectionA Magnets Zd. are magnetizedwith their endsof the same `'magnetic polarity, the opposite magnetic pole being situatediatthe central portion of each magnet. The two magnets tare*v substantially identical bothk as toj dimensions and magnetiza# either to pole piece I or pole piece I6 depending upon which has the greater magnetic strength. This can be controlled at will by appropriate energization of Winding II. Upon energization with direct current of one polarity, one end of core I3 will assume the same polarity as the ends of the permanent magnets 24 and the magnetic ux through its associated pole piece will thereby be increased. The opposite end of the core I3 will have a magnetic polarity the same as that of the permanent magnet centers and the ux through the pole piece associated with this end of core I3 will be decreased. Accordingly, armature `2|) will be attracted to the magnetically stronger pole. In the absence of a restoringspring, armature will remain in this attracted position upon deenergization of winding II.

Winding II may consist of two separate windings which rnay be connected in separate electrical circuits for differential operation, or it may be. provided with a center tap, if desired, for operation of similar character. Where a precise magnetic balance is desired, the two separate windings may be derived by the use of paired wire. If a differential bridge circuit is lto be used, quadded wire may be utilized to obtain fourseparate windings balanced both as to resistance and inductance and having substantially identical turn distribution. Such arrangements are commonly used in polarized relays for duplex telegraphic service.

rIfhe armature positioning mechanism comprises a pair of vhelical compression springs 24 disposed symmetrically with respect to armature pivot pin 23 Qn opposite sides thereof. At their upper ends,y springs 24' engage lock nuts 25 carried by threaded studs v26. At their lower ends, springs 24 engage cup washers 21 through which studs'z pass freely. 'Ihe rounded lower convex surfaces of cup washers 21 engage beveled peripheral portions of apertures 28 in a stationary transverse plate 29.

Studs `2t are threadedly secured in armature members 2| and 22 and are provided at their lower extremities with lock nuts which hold the studs 26 securely against rotation. Each stud 2E is provided with a collar-like portionSI which is adjustable in height by rotation of the entire stud, lock nuts 30 having previously been loosened. If exactly symmetrical adjustment is desired studs 26 are carefully adjusted so that with armature 2U in its central position, the two collar-like portions 3| are just in engagement with the bottoms of the two cup washers 21, or they may engage the cup washers 21 with equal slight pressures. In the event, however, that the degree of engagement between collars 3| and washers 21 should be insuncient to picl; up the full pressure of the compression springs 24' with the armature in its central angular posifreely without opposition from the springs. Ordinarily, the full pressure of either of the compression springs 24 will oppose any appreciable angular displacement of armature 20. With the armature in its normal, or neutral position the upward forces exerted by springs 24 on lock nuts 25, and hence on studs 26 are either substantially Zero or substantially equal and therefore produce no effective torque. Any appreciable angular displacement of armature 2U will therefore pick vup the full force of one or the other of the springs while the other will be rendered wholly ineffective being carried in its entirety by armature '20. This will leave the full compressiveforce of the other spring 24 completely unbalanced and hence acting with its full effect to oppose movement of the armature.

As an alternative adjustment, one of the studs may be adjusted to permit its spring to apply force to the armature throughout its entire range of angular travel. /The other stud is then adjusted to permit itssp'ring to engage the armature at approximatelythe midpoint of its travel with an initial force of about twice the initial pressure used in the symmetrical adjustment described above. 'It may also be desirable to use a spring in the latter position having a somewhat greater vstiiness thanfthe stiffness of the rst spring. The resulting performance is substantially the same as for the symmetrical adjustment. y

It will be thus seen that armature 20 will'remain in its central angular position until an unbalanced force sufficient to overcome the effective resistance ofl either of the compression springs 24 is applied to one of the ends of the armature. The amount of such vforce required may be determined in part` by the selection of appropriate dimensions for the compression ysprings and it may be adjusted to a'certain extent by the positioningl oflock nuts 25 at the upper'ends of studsZS. This resistance of the compression springs is at least suflicient so that the magnetic attraction produced by'permanent magnets 24 at either end of the armature will not overcome the initial spring loading in the event of a slight angular displacement of armature 20 from its-central position. If armature 2e is to be self-restoring upon deenergization 'of winding I, each spring 24 must exert a force suiicient'to overcome 'the residual force of magnets 24 at the position of' extremedisplacement cf yarmature 20- permitted in the particular case in question, and in the absence of magnetic influence from corev i3. The magnitude of this initial spring loading will also'serve tovdetermine the amount of magnetic influence incore I3 required to vcause appreciable.displacement of armature 20 andhence determine the operating tion, then there will be a slight range of angular displacement in which the armature may move characteristicsof the relay.

A modied form of positioningmechanism is shown in Figs.' 6 and 7. A pair of-hollow cylinders 35 are threaded both externally and internally. An adjusting screw 36 engages 4the inter- 'Y nal Athreads of eachcylinder {i5-and the-external threads engage armature'ZIl. Within each threaded cylinderv 35 is a, helical compression spring 31 whichlatits upper'end encircles a-projecting central stud portion 38-`of the adjusting screw At its lower end each rspring 31 eng-ages a spherical ballW 39,` exertingr a downward thrust uponv lthe uppersurface thereof. The extreme lower portion-lbfl eachcylinder 35is inwardly ared to retain ball-39. The' lowerwsurface of each ball 39 is positioned for engagement with full initial load of either ofthe springs 31 -is picked up when armature 20 has been angularly displaced byany very small amount. The dimensioning ofsprings 31 is also governed by the same factors as those which apply to springs 24. The anglev of travel of armature 20 is limited in a clockwise direction by anadjusting screw 40 and in a counter-clockwise direction by a similar adjusting screw 4I. Screws 40 and 4I are symmetrically disposed with respect to armature pivot pin 23. The lower ends of screws-40 and il extend through armature 20 for engagements with the upper surfaces of p ole pieces I5 and I6 respectively. Screws 4|! and 4I are shown provided with lock nuts 42 to secure them in fixed positions of adjustment. Ordinarily, s crews.4ll and 4I will be of non-,magnetic material in order to provide a magnetic gap when armatureZIl is at either of its limits of angular displacement.

insulated at theirlower ends from armature by thin spacers 56 of insulating material interposed between the under surfaces of blocks 53 and varmature 2i). Blocks 53 and spacers 56 are shown held in engagement With armature 20 by the lock nuts 42 associated with adjustable arma-- versecontact-carrying portion or head 55. Se-

The amount of magnetic gap atthe limits of armature travel will determine to a considerable extent the vamount of residual force which will be exerted on the armature tending to retain thearmature in its displaced position. Thisr residual force is produced principally by the permanent magnets 2t, although to some slight extent it may be increased by effects of remanence in themagnetic structure. By appropriate adjustment of screws and 4I and compression springs 24',- the armature may be made either self restoring or it may be caused to remain in'itsdis#- placed conditionby the action of residual 'magnetic forces. The effects of remanence in the magnetic structure are generally undesirable. These may be minimized by the use of-suitable magnetic materials such, for example, as a ferronickel alloy, properly annealed.

The remainder of the structure whichfserves to form a complete relay comprises a plurality of xed contacts 43 carried by brackets 44 which are shown provided with holes 45 for convenience in attaching wires. Brackets 44 are secured to blocks of insulating material 46 byrivets 4'I. Blocks 46 are in turn secured tov-pole pieces I5 and I6 by screws I1. The fixed contact position may be adjusted by loosening one: of the screws I1, positioning the block 45 to provide the desired condition of adjustment and then tightening the screw I'I to maintain-'the adjustment. Pole pieces I5 and I6 are provided with flange portions 48 to which are secured apair of non-magnetic side plates 49 covered by further side plates 5U of insulating material.. Side plates 49 are shown with inwardly bent portions 5I mounting feet for the relay. Insulating sideplate 50 carries a plurality of electrical termi-- nals 52 which may be used for the connectionof conductors extending to operating windingY I I..

- Disposed at opposite ends of armature 20 are a pair of insulating blocks 53 which carry flat flexible spring members 54 secured thereto by a plurality of rivets 55. The rivets 55 yare shown.,w

having holes therein which provide",

cured to each portion 56' is a bridging contact plate 57. Spring member V54k extends freely through pierced slots in contact-carrying portion 55under an offset part 51 of lsaid portion. OW.- ing tothe Ilexibilty of the narrow part of member 5d' this construction provides'veryfreeangular articulation to compensate for the possibility of one fixed contact being higher than the'other. `The stiffer spring 54 provides the necessary resistance to insure good contact between the plate 57 and fixed contacts. .Each of the transverse contact-carrying plates is arranged to establish contact between two adjacent stationary contacts t3 when urged into engagement therewith by angular displacement of armature 2li. With the contacts in engagement, the action of restoring springs 24 will be aided by the force resulting from ilexure of spring members 54 as'indicated y in Fig. 5. This fiexure also causes a certain amount of sliding action or wiping between the fixed and stationary contacts thus tending to Vmake the contact surfaces seli.l cleaning.

Although the relay is shown with a contact arrangement which will close-two electrically independent circuits in each of the two operated positions, other and different contact arrangements may be provided in a manner well known in the art. Where it is advantageous to establish connection directly to movable contact members, flexible conductors extendingk to such contact members may conveniently be terminated at electrical terminals carried by side plate 5B 'such as terminals 52.

The efficiency of the magnetic circuit comprisn ing the permanent magnets 24 is increased by a transverse magnetic member 58 which extends between the central pole areas of the magnets 2d `and is positioned in close proximity to the under side of the armature 25;. A relatively stiif resilient curved spring member 59 is secured to the under side of transverse magnetic member 58 by a rivet 55 and tends to maintain magnets 24 securely in fposition.

Armaturepivot pin 23 is journaled in side plates 49 at 6I, being securely held between the armature members 2i and 22. This permits all bearing actionto be confined tothe ends of pivot pin 23 thereby. increasing the lire of the bearings and also tend-ing to reduce friction. `Sid-e. plates 49,

which arenon-magnetic, may bek of brass and pivot pin'23 may be of steel thus providing suitable bearing materials for the minimizationof wear; y

The magnetic structure illustrated, as noted above, iscapable of adjustment for snap action :operation The force curves which prevail in ,known polarizedrelay structures having centered .armatures are illustrated in Fig. 8 in which the "dashed line EI illustrates the restoring force provided by the usual restoring spring and the curve 182 representsrv the operating ytorque produced by the magnetic structure. The abscissae represent .angularldisplacement.of the armature and the ordinates represent torque acting on the armature.' The vertical lines 83 and 84- represent-the limits of'angular displacement of the armature. Heavy curve 85 which represents the resultant of the magnetic forces and the forces exerted by a restoringspring ofthe designs used in relays of the character referred to, plus dashed parallel curves, indicates that with an increasing current a new equilibrium is established at point 0, and the armature will change itsposition as the current increases in a manner similar to the needle of a milliammeter. As a result, contact closure will take place with zero contact pressure and no appreciable contact pressure can bev obtained un-` til the energizing current has increased substantially above the minimumV current required to effect contact closure. As a result, there is a range of current `values in which the contact pressure will be unsatisfactory and in which contact chattering will occur, especially under conditions of mechanical vibration of the entire magnetic structure.

Referring to Fig. 9, it will beA seen that the armaturev positioning mechanismv of the present invention changes the operating characteristics considerably from those of the conventional relay. The dot-dash line 9| represents the torque of the restoring springs. Curve 92 represents the magnetic torque as in the case of Fig. 8. The heavy line 93 represents the resultant of the spring forces and the magnetic forces. The arrangement of the springs 2d' of the relay is' such that no angular displacement of the armature 20 can occur until a torque suiiicient to overcome the initial loading of the. springs'ZA" hasv been applied to the armature. This minimum torque is indicated at points 95 and 85. TheY curves also indicate that thel rate ofi increase of the magnetic torque is greaterV than the'rate' of increase of the opposing spring torque'. As a result, once the magnetic torque is sunicient to overcome the initial loading torquey producedv by the springs, the armature will moveimmediately to its limit of travel. To releasethe armature of the relay, the operating current isreduced to a point wherethe magnetic torque canfjust be cvercome by the spring torque; Once thisA condition has been attained and the armature starts to return to its normal position, as themagnetic torque will decrease more rapidly than the spring torque, the armature will move immediately to its normal or neutral position. There will'not bev any stable condition of zero Contact pressure since the armature will be ready to return completely to its normal position as soon as the magnetic torque is reduced to a value just slightly less than spring torque. Y

This effect is illustrated in Fig. 10, in'which the spring torque has beendrawn reversed in order to facilitate a comparison of the characteristi'csiwith those of the magnetic torque. The'dot-dash line lill represents the spring torque,.drawn'reversed. Curve |02 represents the magnetic torque with-'no magnetic influence from operating winding. Il.

Curve |03 represents a displacement of curve |02- by a current flow in operating windingY suincient to cause operationof the relay armature in a clockwise direction. At the limit of armature travel represented by vertical line |04, it will be seenY thatthe magnetic torque of curve |03 exceeds the spring torque represented by dotted line by a substantial amount. This excess is available for the production of contact pressure without further increase in the operatingk current; Upon a decreaseV in operating current-sufiicientto .bring the magnetic torque characteristic to the position indicated by curve |05, the magnetic torque will' be just slightly less than the spring torquei- Y. The spring' torque will immediately` take control. and restore the armature to itsnorrnal or neutral position. It will be noted, that as the armature proceeds toward its normal position, the spring l torque represented by line |0`| eiceeds' vthe magnetic torque of |05 a continually increasingt amount. This Vcauses the release of the relay armature to talepla'ce ina positive manner and avoids thepres'ence of an undesirable stable condition,; 9fsubstantially nero contactpressure.

llhavedshownwhatl believe to bethe bestembodimentsof my i'nventio'n.v Il do not wish, however, to be confined to the'embodinients shown but whatlj desire to covery by Letters Patent is set forth in the appendedclaims.

1 Inv adevice of the class described, af inagnetizable. core, a pair'of` polepieces operatively associated` with the. ends of the core, an operatingwinding on the coredispos'edintermediate the pole p iecesf,'aY centrally pivoted armature having its ends'in'lresponsive proximity to the polepieces, andn an elongated'- magnetized member extending-parallel to andlin operative proxim-ityto' the armature having-a magnetic pole area substantially midway of.' its length arranged to influence the armature .near the. center thereof and two Dole-areasatitslends of'polarity opposite"y to thatof-the intermediate ple'V area arranged to inuence the pole pieces with like polarity and 13o-substantially equal'- degree, whereby the position-ofthe arma-ture may beselectively controlled by appropriate` .energi'zation' of the operating winding,4 said operating winding beingy of substantially circular cross section, aA framework for supporti-ng the roperating winding, core', vpole pieces,armature and elongated magnetied member, said framework providing a space of substantiallyrectangular cross section for accommodation of the operating winding-and magnetizedv member, said magnetizedmember being of substantiallytriangular cross section and means for supporting the same in a cornerof'the rectangular-space inwhich the operatingv windingis mounted with thevertex of the-triangle in proximity to such corner, and with the long side of the triangle-.in proximity to the 'circumference of theoperating winding ,2;-A-device, as in claiml in which the magnetized member isa permanent magnet. -v

3g A-device as claimed in claimlin which-two magnetized members are provided supported in ada'acent ornersof said rectangular space adjacent to theside of thespace -nearest to the armatural said-magnetized members being permanent magnets, andl a bridge'fofrmagnetizable material connecting-saidmagnets near the centers thereof.

4. Infan; electromagnetic relay selectively responsive tothe-magnitude' and polarity of an f 'energizing-'current' applied to an voperating'windthereon andwhaving its opposite ends" securedto the pole pieces, an elongated magnetized'membernmountedfin said= frame and extending be- .titfeerrv `said-pele.l pieces substantially parallel to ,the` operating winding andin proximity thereto,

and'havingacentral magnetic area of one polarity and-end-magnetic areas of oppositepolarity, a magnetizable armature pivotally supported .near-its center of gravity on said-framethe armature, when in neutral position, extending symmetrically into magnetically responsive proximity to the pole pieces, and preloaded spring means associated with the armature for resistingmovement thereof towards either pole piece until a predetermined iiux has beenbuilt up, said spring means comprising spring holding sleeves adjustably mounted on the armature at opposite sides of the pivotal support thereof, springs mounted in said sleeves, adjustable abutment means carried by said sleeves for preloading said springs, movable abutments mounted in said sleeves and engaging said springs, said sleeves and abutments being provided with coacting formations permitting movement of said abutments relatively to said sleeves in a direction to increase the load on said springs but limiting movement of said movable abutments in the opposite direction, and fixed abutment surfaces carried by the frame with which the movable abutments are normally in engagement when the armature is in neutral position, movement of the armature out of neutral position under the influence of the energizing current causing the spring carrying sleeve at one side of the armature pivot to move towards the corresponding fixed abutment surface, thereby increasing the load on the spring carried in said sleeve, the spring carrying sleeve at the other side of the armature pivot simultaneously moving away from the corresponding abutment surface and carrying the movable abutment member therein out of engagement with said surface.

5. In an electromagnetic relay selectively responsive to the magnitude and polarity of an energizing current applied to an operating winding thereof, a magnetizable core with an operating winding thereon, magnetizable pole pieces fixed to the ends of said core, a pair of non-magnetic frame members fixed to said pole pieces on opposite sides of said core, an elongated permanent magnet mounted between said frame members and extending between said pole pieces substan- 1 tially parallel with the operating Winding and in proximity thereto, and having a central magnetic area of one polarity and end magnetic areas of opposite polarity, a magnetizable armature pivotally supported near its center of gravity between said frame member, the armature, when in neutral position, extending symmetrically into magnetically responsive proximity to the pole pieces, and preloaded spring means for resisting movement of the armature towards either pole piece until a predetermined flux has been built up, said spring means comprising a pair of adjustable spring devices, one for resisting movement of said armature in one direction, and the other for resisting movement of the armature in the other direction, each of said devices including a spring, adjustable holding means for the spring by which the spring may be restrained in adjustable preloaded condition, a movable spring pressed engagement member, stop means on the spring holding member limiting movement of said engagement member in one direction, said engagement member being movable away from said stop means in a direction to increase the stress on the spring, and abutments for engagement with the engagement members of said spring devices, said spring devices and abutments constituting pairs of reacting elements mounted for relative movement, one pair of said elements being mounted on the movable armature and the other pair of said elements being mounted on a stationary support, whereby upon movement of the armature in either direction one of said engagement members will be moved away from its corresponding abutment while the other element will be moved so as to increase the tension of its spring, said engagement members being normally balanced in engagement with their corresponding abutments when the armature is in neutral position.

RICHARD T. FISHER.

REFERENCES CITED The following references are of record in the nie of this patent:

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